BRIDGEPORT -- A fire in a multi-unit home on North Avenue displaced eight city residents on Friday.

Assistant Fire Chief Robert Morton said the fire, which began about 4:20 p.m., did not injure any of the residents of 1455 North Ave. or responding firefighters, but it did leave the three-story building uninhabitable.

The cause and exact origin of the fire remained under investigation Friday, although Morton said it appeared to have started on the second floor and then travelled up the building's rear exterior wall before burning its way inside the structure.

"Once it burned its way inside, it ran right up to the third floor," he said.

Firefighters climbed onto the structure's roof, the rear portion of which was burned out, in their efforts to pick away at hot spots and douse the flames.

Morton said the home's second and third floor suffered the worst damage, which included extensive fire damage.

City police closed North Avenue to traffic between Lexington and Madison avenues for more than an hour while firefighters worked on the blaze.